I never understood why this is an acceptable thing to do. It's democracy except you get to pick who votes for you and who doesn't, so, it's actually not.
The United States isn't a democracy, it's a republic.
It's a democratic republic, to be specific. Republicanism is the form of the government (representation of the people), democratic elections are the mechanism of selecting those representatives. You could have, e.g. a technocratic, plutocratic, or a constitutional monarchial republic.
Right, the point is we still have a choice in who represents us, or what appears to be the illusion of a choice.